In blow molding or stretch-blow molding, at least the mold parts (mold halves) forming the wall regions of the container are usually received in mold support shells. The mold support shells normally also fulfill the function of controlling the temperature of the blow mold. To this end, channels through which a temperature control medium (water, oil) flows can be formed in the mold support shells. A usually two-part mold support is provided for fixing the mold support shells, the mold support producing the retaining function for the mold support shells and primarily serving to withstand the forces during the blow molding process. Especially the task of withstanding forces requires an extraordinarily stable design of the bearing of the mold support parts, the bearing also serving to open and close the blow mold. Furthermore, locking elements are provided in most cases in the front region of the mold support parts which, just as the bearing in the rear region, withstand the forces from the blow molding process. The mold support parts also have to be designed to be very stable and thus to have large dimensions because superimposed tensile stresses and bending stresses must be received. In this embodiment, however, the blow mold can possibly nevertheless minimally deform under the forces. The consequence would be a visible parting seam at the manufactured container. To prevent the mold parts from opening minimally, a mold support shell can be floatingly held in its mold support part, and a separate compensation element can act upon it to compensate the total deformation and inflexibly keep the mold parts together.
In the blow mold known from US 2010/0047375 A1, the locking means comprises a sleeve guided at a support in a linearly shiftable manner, where a collar closed in the circumferential direction is mounted at the edge of the sleeve situated at the front, seen in the direction in which the sleeve is slid onto the mold support shells. The mold support shells containing the mold parts can be swiveled about an axis situated underneath the blow mold and being oriented approximately radially with respect to the blow rotor axis and comprise clamps in the form of bow segments at reinforced outer wall areas, or outer wall areas provided with reinforcing ribs, the clamps defining externally conical pressing surfaces onto which the collar is slid to lock the blow mold and to support the mold parts against forces from the blow molding process. The conical pressing surfaces are only present in areas of upper parts of the mold support shells limited in the direction of the mold cavity axis, so that the locking pressure generated by the collar only acts on the mold support shells in a very restricted area. As the locking pressure of the collar thus locally acts on the mold support shells, and in the circumferential direction also only within limits, the mold support shells are reinforced above and underneath the conical pressing surfaces. The motion drive of the locking means is cam-controlled. The sleeve surrounding the bottom parts of the mold support shells and supporting the collar contains motion links in which cams of the mold support shells move when the collar is being slid onto the conical mating surfaces. The cams control the closing and opening of the blow mold. The mold parts are mounted in the mold support shells so as to be replaceable. Inside the sleeve supporting the collar, a bottom mold with its driving mechanism is accommodated. Due to the required reinforcements of the mold support shells and the complex locking means, heavy masses have to be quickly moved during the open, closing, and locking processes, and very stable motion drives are required. As the locking pressure of the collar acts upon the two mold support shells only in locally restricted areas, there is a risk in that uncontrollable deformations arise at the mold parts under the forces resulting from the blow molding process, whereby the mold parting plane can undesirably show at least in some areas in the manufactured container.
EP 1 980 386 A illustrates an auxiliary locking mechanism in the upper region of the blow mold via metallic cone surfaces at the mold shells and a cone at the blow nozzle placed there. The mold shells are also locked in a conventional manner further at the bottom.